Modeling HF Propagation Around Skyscrapers: Interactive Cesium Maps, F2 Bounces, and Propagation Wedges from One Maritime Plaza

After contacting Alaska from San Francisco on 14.0574 MHz with 5 watts power delivered via a 1/4 wave vertical antenna through an apartment highrise last week, I started building models of HF propagation around buildings. This culminated in several new tools that I'll be discussing in more depths in future posts and the propagation map you can interact with towards the bottom of the page.

What's in the Map

Radio Contact Paths

The map shows the QSOs (radio contacts) I made from the park on the top of One Maritime Plaza. Each contact is mapped out by a solid line running along the ground as well as a likely path the high frequency radio signal took as it bounced off the ionosphere on its way to the receiving station. I've talked about mapping F2 bounces before.

Fun F2 paths near a moutain outside El Paso, TX

The paths in the map below use the maximum F2 layer height of the ionosphere at the time of the contact as it was reported by NOAA Glotec data. If you'd like to see a Cesium map of the most recent F2 data, you can find that here.

The QSOs in the map are anchored at the location of the ham radio transmitter I used to make them.

3-D Propagation Wedges

This brings us to actual RF modeling. You can see three propagation sky maps, (aka propagation wedges), at radii of 250, 500, and 1000 meters out from the transmitter site in the map below.

Each wedge is an interference pattern generated by summing the electrical field contributions of the radio's antenna output with the fields from antenna RF that was reflected or diffracted from nearby buildings. The patterns in the map are from the set of buildings surrounding my transmitter site shown below. The building outlines won't appear on the interactive map, they're generated by another tool that I'll document very soon.

The image below shows the propagation wedges. Remember, you can actually interact with them directly in the Cesium map at the bottom of the page.

You can clean up a bit of the clutter by using the checkbox panel shown on the right to make wedges visible or hide them.

Each point on the wedge is labeled with its relative field strength in the propagation pattern as a whole

The Unintentional Easter Egg Feature

If you click on a QSO line, after a bit, the empty right hand panel of the map will populate with elevation data from the USGS Elevation Point Query Service. I, personally, find it fascinating that trees throw off the ground detection a bit, but I digress.

Ground elevation map of the path from the transmitter to Colorado.

And, Finally, the Map

Almost. Let's talk caveats first.

The map is not exact. The building materials used for construction of the structures surrounding the transmitter site are—so far—unknown, so estimates were made. Each reflective or diffractive surface is modeled to re-emit waves that reach the observation point independent of other obstacles in their path. Compensating for this is one of the future steps of this project.

I've reviewed the code. It's using a free-space Green's function spherical wave to model the antenna source. Speaking of that, the antenna is modeled by being divided into 21 segments.

The Map

Related Posts in this Series

Fun with GPT-5 and HF Propagation Analysis (Model Verification)

Urban POTA in Downtown San Francisco, So Many Building, So Many RF Obstacles, and So Much Fun!

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